Polyamide resins are used in various fields such as automobile parts and electric parts and electronic parts by utilizing superiorities in mechanical characteristics, electric characteristics, chemical resistance, molding processability, resistance to soldering heat and the like. Above all, polyamide resin compositions comprising a melamine cyanurate-based flame retardant as a flame retardant having no halogen are broadly used in the fields requiring flame retardancy and resistance to soldering heat as in electric parts and electronic parts such as connectors.
In recent years, connector applications have demanded materials meeting the fire hazard testing according to the IEC 60695-2-11 standard and the IEC 60695-2-13 standard, which require higher flame retardancy levels. However, the present situation is such that polyamide resins used in connector applications do not satisfy these requirements.
Patent Document 1 discloses that a flame retardant polyamide resin molding material obtained by mixing a flame retardant polyamide resin composition pellets containing melamine cyanurate with a polyamide resin pellets in order to improve the toughness of molded articles after molding suppresses the occurrence of silver streaks and improves the appearance.
Patent Document 2 discloses that a flame retardant polyamide resin composition containing a polyamide resin, a triazine-based flame retardant and a carboxylic acid amide-based wax improves the glow wire ignition temperature. Patent Document 3 discloses a composition for molding containing a non-branched thermoplastic polyamide, melamine cyanurate, a flame retardant containing nitrogen other than melamine cyanurate, and a phosphate-based flame retardant.
Further, Patent Document 4 discloses that a flame retardant polyamide resin composition obtained by melt-kneading a masterbatch obtained by melt-kneading a polyamide resin and melamine cyanurate, with a polyamide resin, is excellent in mechanical characteristics such as elongation at tensile break.
Still further, Patent Document 5 discloses a technology for treating the surface of fine melamine cyanurate with a specific additive to suppress reaggregation.    Patent Document 1: Japanese Patent Laid-Open No. H11-302536    Patent Document 2: Japanese Patent Laid-Open No. 2005-171232    Patent Document 3: National Publication of International Patent Application No. 2008-512525